Reference signal reception method in wireless communication system, and device for same

ABSTRACT

According to one embodiment of the present invention, a method by which a terminal receives a reference signal for determining a position in an unlicensed band in a wireless communication system can comprise the steps of: receiving positioning reference signal (PRS)-related configuration information transmitted through the cooperation of one or more unlicensed band cells, wherein the PRS-related configuration information includes information on a plurality of sub-bands in the unlicensed band, in which the PRS is transmitted, and information on a PRS transmission period for each of the plurality of sub-bands; receiving and measuring the PRS by using the PRS-related configuration information; and reporting the PRS measurement result to a serving cell.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method of receiving a reference signal in awireless communication system and an apparatus therefor.

BACKGROUND ART

Recently, various devices requiring machine-to-machine (M2M)communication and high data transfer rate, such as smartphones or tabletpersonal computers (PCs), have appeared and come into widespread use.This has rapidly increased the quantity of data which needs to beprocessed in a cellular network. In order to satisfy such rapidlyincreasing data throughput, recently, carrier aggregation (CA)technology which efficiently uses more frequency bands, cognitive ratiotechnology, multiple antenna (MIMO) technology for increasing datacapacity in a restricted frequency, multiple-base-station cooperativetechnology, etc. have been highlighted. In addition, communicationenvironments have evolved such that the density of accessible nodes isincreased in the vicinity of a user equipment (UE). Here, the nodeincludes one or more antennas and refers to a fixed point capable oftransmitting/receiving radio frequency (RF) signals to/from the userequipment (UE). A communication system including high-density nodes mayprovide a communication service of higher performance to the UE bycooperation between nodes.

A multi-node coordinated communication scheme in which a plurality ofnodes communicates with a user equipment (UE) using the sametime-frequency resources has much higher data throughput than legacycommunication scheme in which each node operates as an independent basestation (BS) to communicate with the UE without cooperation.

A multi-node system performs coordinated communication using a pluralityof nodes, each of which operates as a base station or an access point,an antenna, an antenna group, a remote radio head (RRH), and a remoteradio unit (RRU). Unlike the conventional centralized antenna system inwhich antennas are concentrated at a base station (BS), nodes are spacedapart from each other by a predetermined distance or more in themulti-node system. The nodes can be managed by one or more base stationsor base station controllers which control operations of the nodes orschedule data transmitted/received through the nodes. Each node isconnected to a base station or a base station controller which managesthe node through a cable or a dedicated line.

The multi-node system can be considered as a kind of Multiple InputMultiple Output (MIMO) system since dispersed nodes can communicate witha single UE or multiple UEs by simultaneously transmitting/receivingdifferent data streams. However, since the multi-node system transmitssignals using the dispersed nodes, a transmission area covered by eachantenna is reduced compared to antennas included in the conventionalcentralized antenna system. Accordingly, transmit power required foreach antenna to transmit a signal in the multi-node system can bereduced compared to the conventional centralized antenna system usingMIMO. In addition, a transmission distance between an antenna and a UEis reduced to decrease in pathloss and enable rapid data transmission inthe multi-node system. This can improve transmission capacity and powerefficiency of a cellular system and meet communication performancehaving relatively uniform quality regardless of UE locations in a cell.Further, the multi-node system reduces signal loss generated duringtransmission since base station(s) or base station controller(s)connected to a plurality of nodes transmit/receive data in cooperationwith each other. When nodes spaced apart by over a predetermineddistance perform coordinated communication with a UE, correlation andinterference between antennas are reduced. Therefore, a high signal tointerference-plus-noise ratio (SINR) can be obtained according to themulti-node coordinated communication scheme.

Owing to the above-mentioned advantages of the multi-node system, themulti-node system is used with or replaces the conventional centralizedantenna system to become a new foundation of cellular communication inorder to reduce base station cost and backhaul network maintenance costwhile extending service coverage and improving channel capacity and SINRin next-generation mobile communication systems.

DISCLOSURE OF THE INVENTION Technical Task

A technical task of the present invention is to provide a method ofreceiving a reference signal in a wireless communication system and anoperation related to the method.

Technical tasks obtainable from the present invention are non-limitedthe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, accordingto one embodiment, a method of receiving a reference signal forpositioning in an unlicensed band, which is received by a terminal in awireless communication system, includes receiving positioning referencesignal (PRS)-related configuration information transmitted through thecoordination of one or more unlicensed band cells, wherein thePRS-related configuration information includes information on aplurality of subbands within the unlicensed band on which the PRS istransmitted and information on a PRS transmission period for each of theplurality of the subbands, receiving and measuring a PRS using thePRS-related configuration information, and reporting a measurementresult of the PRS to a serving cell.

Additionally or alternatively, the receiving and measuring the PRS mayinclude performing PRS blind detection using the PRS-relatedconfiguration information.

Additionally or alternatively, the method may further include receivinginformation on the number of subbands on which the PRS blind detectionis to be performed.

Additionally or alternatively, the method may further include receivinginformation on priority of a subband on which the PRS blind detection isto be performed.

Additionally or alternatively, the information on the PRS transmissionperiod may be common to unlicensed band cells belonging to the same cellgroup.

Additionally or alternatively, the information on the PRS transmissionperiod may include a transmission period, offset, or a burst length ofthe PRS.

Additionally or alternatively, the PRS-related configuration informationmay include information on whether or not the PRS transmission periodbelongs to channel occupation time for the one or more unlicensed bandcells.

Additionally or alternatively, the receiving and measuring the PRS mayinclude performing PRS blind detection during the channel occupationtime.

Additionally or alternatively, the PRS-related configuration informationmay include information on the channel occupation time and informationon the PRS transmission period.

Additionally or alternatively, the PRS-related configuration informationmay be received through downlink control information via a licensed bandcell or an unlicensed band cell.

Additionally or alternatively, the method may further includedetermining that a PRS transmission subframe belongs to channeloccupation time for the one or more unlicensed band cells if areservation signal is received in a specific time period.

Additionally or alternatively, a PRS transmitted through the one or moreunlicensed band cells may be transmitted on a resource element where adifferent unlicensed band cell does not transmit a PRS.

Additionally or alternatively, the measurement result of the PRS may beindependent of a PRS measurement result on a licensed band.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a different embodiment, aterminal configured to receive a reference signal for positioningthrough one or more unlicensed band cells in a wireless communicationsystem includes an radio frequency (RF) unit and a processor controlsthe RF unit, wherein the processor receives positioning reference signal(PRS)-related configuration information transmitted through thecoordination of one or more unlicensed band cells, wherein thePRS-related configuration information includes information on aplurality of subbands within the unlicensed band on which the PRS istransmitted and information on a PRS transmission period for each of theplurality of the subbands, receives and measures a PRS using thePRS-related configuration information, reports a measurement result ofthe PRS to a serving cell.

Technical solutions obtainable from the present invention arenon-limited the above-mentioned technical solutions. And, otherunmentioned technical solutions can be clearly understood from thefollowing description by those having ordinary skill in the technicalfield to which the present invention pertains.

Advantageous Effects

According to one embodiment of the present invention, it is able toefficiently receive and measure a reference signal in a wirelesscommunication system.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a diagram for an example of a radio frame structure used in awireless communication system;

FIG. 2 is a diagram for an example of a downlink (DL)/uplink (UL) slotstructure in a wireless communication system;

FIG. 3 is a diagram for an example of a downlink (DL) subframe structureused in 3GPP LTE/LTE-A system;

FIG. 4 is a diagram for an example of an uplink (UL) subframe structureused in 3GPP LTE/LTE-A system;

FIG. 5 is a diagram for a structure of transmitting a PRS;

FIGS. 6 and 7 are diagrams for RE mapping of a PRS (positioningreference signal);

FIG. 8 is a diagram for an example of an LBT (listen before talk)-basedchannel access operation according to a FBE (frame based equipment);

FIG. 9 is a diagram for an example of an LBT (listen before talk)-basedchannel access operation according to an LBE (load based equipment);

FIG. 10 is a diagram for an example of configuring a subframe (orpositioning occasion) in which a PRS is transmitted according to oneembodiment of the present invention;

FIG. 11 is a diagram for a plurality of subbands constructing anunlicensed band and CCA performed in a plurality of the subbandsaccording to one embodiment of the present invention;

FIG. 12 is a diagram for a configuration of a subframe in which a PRS istransmitted according to one embodiment of the present invention;

FIG. 13 is a flowchart for an operation according to one embodiment ofthe present invention;

FIG. 14 is a block diagram for a device for implementing embodiment(s)of the present invention.

BEST MODE Mode for Invention

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The accompanying drawings illustrate exemplary embodiments ofthe present invention and provide a more detailed description of thepresent invention. However, the scope of the present invention shouldnot be limited thereto.

In some cases, to prevent the concept of the present invention frombeing ambiguous, structures and apparatuses of the known art will beomitted, or will be shown in the form of a block diagram based on mainfunctions of each structure and apparatus. Also, wherever possible, thesame reference numbers will be used throughout the drawings and thespecification to refer to the same or like parts.

In the present invention, a user equipment (UE) is fixed or mobile. TheUE is a device that transmits and receives user data and/or controlinformation by communicating with a base station (BS). The term ‘UE’ maybe replaced with ‘terminal equipment’, ‘Mobile Station (MS)’, ‘MobileTerminal (MT)’, ‘User Terminal (UT)’, ‘Subscriber Station (SS)’,‘wireless device’, ‘Personal Digital Assistant (PDA)’, ‘wireless modem’,‘handheld device’, etc. A BS is typically a fixed station thatcommunicates with a UE and/or another BS. The BS exchanges data andcontrol information with a UE and another BS. The term ‘BS’ may bereplaced with ‘Advanced Base Station (ABS)’, ‘Node B’, ‘evolved-Node B(eNB)’, ‘Base Transceiver System (BTS)’, ‘Access Point (AP)’,‘Processing Server (PS)’, etc. In the following description, BS iscommonly called eNB.

In the present invention, a node refers to a fixed point capable oftransmitting/receiving a radio signal to/from a UE by communication withthe UE. Various eNBs can be used as nodes. For example, a node can be aBS, NB, eNB, pico-cell eNB (PeNB), home eNB (HeNB), relay, repeater,etc. Furthermore, a node may not be an eNB. For example, a node can be aradio remote head (RRH) or a radio remote unit (RRU). The RRH and RRUhave power levels lower than that of the eNB. Since the RRH or RRU(referred to as RRH/RRU hereinafter) is connected to an eNB through adedicated line such as an optical cable in general, cooperativecommunication according to RRH/RRU and eNB can be smoothly performedcompared to cooperative communication according to eNBs connectedthrough a wireless link. At least one antenna is installed per node. Anantenna may refer to an antenna port, a virtual antenna or an antennagroup. A node may also be called a point. Unlike a conventionalcentralized antenna system (CAS) (i.e. single node system) in whichantennas are concentrated in an eNB and controlled an eNB controller,plural nodes are spaced apart at a predetermined distance or longer in amulti-node system. The plural nodes can be managed by one or more eNBsor eNB controllers that control operations of the nodes or schedule datato be transmitted/received through the nodes. Each node may be connectedto an eNB or eNB controller managing the corresponding node via a cableor a dedicated line. In the multi-node system, the same cell identity(ID) or different cell IDs may be used for signal transmission/receptionthrough plural nodes. When plural nodes have the same cell ID, each ofthe plural nodes operates as an antenna group of a cell. If nodes havedifferent cell IDs in the multi-node system, the multi-node system canbe regarded as a multi-cell (e.g., macro-cell/femto-cell/pico-cell)system. When multiple cells respectively configured by plural nodes areoverlaid according to coverage, a network configured by multiple cellsis called a multi-tier network. The cell ID of the RRH/RRU may beidentical to or different from the cell ID of an eNB. When the RRH/RRUand eNB use different cell IDs, both the RRH/RRU and eNB operate asindependent eNBs.

In a multi-node system according to the present invention, which will bedescribed below, one or more eNBs or eNB controllers connected to pluralnodes can control the plural nodes such that signals are simultaneouslytransmitted to or received from a UE through some or all nodes. Whilethere is a difference between multi-node systems according to the natureof each node and implementation form of each node, multi-node systemsare discriminated from single node systems (e.g. CAS, conventional MIMOsystems, conventional relay systems, conventional repeater systems,etc.) since a plurality of nodes provides communication services to a UEin a predetermined time-frequency resource. Accordingly, embodiments ofthe present invention with respect to a method of performing coordinateddata transmission using some or all nodes can be applied to varioustypes of multi-node systems. For example, a node refers to an antennagroup spaced apart from another node by a predetermined distance ormore, in general. However, embodiments of the present invention, whichwill be described below, can even be applied to a case in which a noderefers to an arbitrary antenna group irrespective of node interval. Inthe case of an eNB including an X-pole (cross polarized) antenna, forexample, the embodiments of the preset invention are applicable on theassumption that the eNB controls a node composed of an H-pole antennaand a V-pole antenna.

A communication scheme through which signals are transmitted/receivedvia plural transmit (Tx)/receive (Rx) nodes, signals aretransmitted/received via at least one node selected from plural Tx/Rxnodes, or a node transmitting a downlink signal is discriminated from anode transmitting an uplink signal is called multi-eNB MIMO or CoMP(Coordinated Multi-Point Tx/Rx). Coordinated transmission schemes fromamong CoMP communication schemes can be categorized into JP (JointProcessing) and scheduling coordination. The former may be divided intoJT (Joint Transmission)/JR (Joint Reception) and DPS (Dynamic PointSelection) and the latter may be divided into CS (CoordinatedScheduling) and CB (Coordinated Beamforming). DPS may be called DCS(Dynamic Cell Selection). When JP is performed, more variouscommunication environments can be generated, compared to other CoMPschemes. JT refers to a communication scheme by which plural nodestransmit the same stream to a UE and JR refers to a communication schemeby which plural nodes receive the same stream from the UE. The UE/eNBcombine signals received from the plural nodes to restore the stream. Inthe case of JT/JR, signal transmission reliability can be improvedaccording to transmit diversity since the same stream is transmittedfrom/to plural nodes. DPS refers to a communication scheme by which asignal is transmitted/received through a node selected from plural nodesaccording to a specific rule. In the case of DPS, signal transmissionreliability can be improved because a node having a good channel statebetween the node and a UE is selected as a communication node.

In the present invention, a cell refers to a specific geographical areain which one or more nodes provide communication services. Accordingly,communication with a specific cell may mean communication with an eNB ora node providing communication services to the specific cell. Adownlink/uplink signal of a specific cell refers to a downlink/uplinksignal from/to an eNB or a node providing communication services to thespecific cell. A cell providing uplink/downlink communication servicesto a UE is called a serving cell. Furthermore, channel status/quality ofa specific cell refers to channel status/quality of a channel or acommunication link generated between an eNB or a node providingcommunication services to the specific cell and a UE. In 3GPP LTE-Asystems, a UE can measure downlink channel state from a specific nodeusing one or more CSI-RSs (Channel State Information Reference Signals)transmitted through antenna port(s) of the specific node on a CSI-RSresource allocated to the specific node. In general, neighboring nodestransmit CSI-RS resources on orthogonal CSI-RS resources. When CSI-RSresources are orthogonal, this means that the CSI-RS resources havedifferent subframe configurations and/or CSI-RS sequences which specifysubframes to which CSI-RSs are allocated according to CSI-RS resourceconfigurations, subframe offsets and transmission periods, etc. whichspecify symbols and subcarriers carrying the CSI RSs.

In the present invention, PDCCH (Physical Downlink ControlChannel)/PCFICH (Physical Control Format Indicator Channel)/PHICH(Physical Hybrid automatic repeat request Indicator Channel)/PDSCH(Physical Downlink Shared Channel) refer to a set of time-frequencyresources or resource elements respectively carrying DCI (DownlinkControl Information)/CFI (Control Format Indicator)/downlink ACK/NACK(Acknowledgement/Negative ACK)/downlink data. In addition, PUCCH(Physical Uplink Control Channel)/PUSCH (Physical Uplink SharedChannel)/PRACH (Physical Random Access Channel) refer to sets oftime-frequency resources or resource elements respectively carrying UCI(Uplink Control Information)/uplink data/random access signals. In thepresent invention, a time-frequency resource or a resource element (RE),which is allocated to or belongs toPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH, is referred to as aPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH RE orPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH resource. In the followingdescription, transmission of PUCCH/PUSCH/PRACH by a UE is equivalent totransmission of uplink control information/uplink data/random accesssignal through or on PUCCH/PUSCH/PRACH. Furthermore, transmission ofPDCCH/PCFICH/PHICH/PDSCH by an eNB is equivalent to transmission ofdownlink data/control information through or onPDCCH/PCFICH/PHICH/PDSCH.

FIG. 1 illustrates an exemplary radio frame structure used in a wirelesscommunication system. FIG. 1(a) illustrates a frame structure forfrequency division duplex (FDD) used in 3GPP LTE/LTE-A and FIG. 1(b)illustrates a frame structure for time division duplex (TDD) used in3GPP LTE/LTE-A.

Referring to FIG. 1, a radio frame used in 3GPP LTE/LTE-A has a lengthof 10 ms (307200Ts) and includes 10 subframes in equal size. The 10subframes in the radio frame may be numbered. Here, Ts denotes samplingtime and is represented as Ts=1/(2048*15 kHz). Each subframe has alength of 1 ms and includes two slots. 20 slots in the radio frame canbe sequentially numbered from 0 to 19. Each slot has a length of 0.5 ms.A time for transmitting a subframe is defined as a transmission timeinterval (TTI). Time resources can be discriminated by a radio framenumber (or radio frame index), subframe number (or subframe index) and aslot number (or slot index).

The radio frame can be configured differently according to duplex mode.Downlink transmission is discriminated from uplink transmission byfrequency in FDD mode, and thus the radio frame includes only one of adownlink subframe and an uplink subframe in a specific frequency band.In TDD mode, downlink transmission is discriminated from uplinktransmission by time, and thus the radio frame includes both a downlinksubframe and an uplink subframe in a specific frequency band.

Table 1 shows DL-UL configurations of subframes in a radio frame in theTDD mode.

TABLE 1 Downlink- to-Uplink Switch- DL-UL point Subframe numberconfiguration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U D S U U U1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms  D S U U UD D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D D D D D 6 5ms D S U U U D S U U D

In Table 1, D denotes a downlink subframe, U denotes an uplink subframeand S denotes a special subframe. The special subframe includes threefields of DwPTS (Downlink Pilot TimeSlot), GP (Guard Period), and UpPTS(Uplink Pilot TimeSlot). DwPTS is a period reserved for downlinktransmission and UpPTS is a period reserved for uplink transmission.Table 2 shows special subframe configuration.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Special Normal cyclic Extended Normal Extendedsubframe prefix in cyclic prefix cyclic prefix cyclic prefixconfiguration DwPTS uplink in uplink DwPTS in uplink in uplink 0  6592 ·T_(s) 2192 · T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s)1 19760 · T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 ·T_(s) 25600 · T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 ·T_(s) 5  6592 · T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 ·T_(s) 23040 · T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — —9 13168 · T_(s) — — —

FIG. 2 illustrates an exemplary downlink/uplink slot structure in awireless communication system. Particularly, FIG. 2 illustrates aresource grid structure in 3GPP LTE/LTE-A. A resource grid is presentper antenna port.

Referring to FIG. 2, a slot includes a plurality of OFDM (OrthogonalFrequency Division Multiplexing) symbols in the time domain and aplurality of resource blocks (RBs) in the frequency domain. An OFDMsymbol may refer to a symbol period. A signal transmitted in each slotmay be represented by a resource grid composed of N_(RB) ^(DL/UL)*N_(SC)^(RB) subcarriers and N_(symb) ^(DL/UL) OFDM symbols. Here, N_(RD) ^(DL)denotes the number of RBs in a downlink slot and N_(RB) ^(UL) denotesthe number of RBs in an uplink slot. N_(RB) ^(DL) and N_(RB) ^(UL)respectively depend on a DL transmission bandwidth and a UL transmissionbandwidth. N_(symb) ^(DL) denotes the number of OFDM symbols in thedownlink slot and N_(symb) ^(UL) denotes the number of OFDM symbols inthe uplink slot. In addition, N_(SC) ^(RB) denotes the number ofsubcarriers constructing one RB.

An OFDM symbol may be called an SC-FDM (Single Carrier FrequencyDivision Multiplexing) symbol according to multiple access scheme. Thenumber of OFDM symbols included in a slot may depend on a channelbandwidth and the length of a cyclic prefix (CP). For example, a slotincludes 7 OFDM symbols in the case of normal CP and 6 OFDM symbols inthe case of extended CP. While FIG. 2 illustrates a subframe in which aslot includes 7 OFDM symbols for convenience, embodiments of the presentinvention can be equally applied to subframes having different numbersof OFDM symbols. Referring to FIG. 2, each OFDM symbol includes N_(RB)^(DL/UL)*N_(SC) ^(RB) subcarriers in the frequency domain. Subcarriertypes can be classified into a data subcarrier for data transmission, areference signal subcarrier for reference signal transmission, and nullsubcarriers for a guard band and a direct current (DC) component. Thenull subcarrier for a DC component is a subcarrier remaining unused andis mapped to a carrier frequency (f0) during OFDM signal generation orfrequency up-conversion. The carrier frequency is also called a centerfrequency.

An RB is defined by N_(symb) ^(DL/UL) (e.g., 7) consecutive OFDM symbolsin the time domain and N_(SC) ^(RB) (e.g., 12) consecutive subcarriersin the frequency domain. For reference, a resource composed by an OFDMsymbol and a subcarrier is called a resource element (RE) or a tone.Accordingly, an RB is composed of N_(symb) ^(DL/UL)*N_(SC) ^(RB)REs.Each RE in a resource grid can be uniquely defined by an index pair(k, 1) in a slot. Here, k is an index in the range of 0 to N_(symb)^(DL/UL)*N_(SC) ^(RB)−1 in the frequency domain and 1 is an index in therange of 0 to N_(symb) ^(DL/UL)−1.

Two RBs that occupy N_(SC) ^(RB) consecutive subcarriers in a subframeand respectively disposed in two slots of the subframe are called aphysical resource block (PRB) pair. Two RBs constituting a PRB pair havethe same PRB number (or PRB index). A virtual resource block (VRB) is alogical resource allocation unit for resource allocation. The VRB hasthe same size as that of the PRB. The VRB may be divided into alocalized VRB and a distributed VRB depending on a mapping scheme of VRBinto PRB. The localized VRBs are mapped into the PRBs, whereby VRBnumber (VRB index) corresponds to PRB number. That is, nPRB=nVRB isobtained. Numbers are given to the localized VRBs from 0 to N_(VRB)^(DL)−1, and N_(VRB) ^(DL)=N_(RB) ^(DL) is obtained. Accordingly,according to the localized mapping scheme, the VRBs having the same VRBnumber are mapped into the PRBs having the same PRB number at the firstslot and the second slot. On the other hand, the distributed VRBs aremapped into the PRBs through interleaving. Accordingly, the VRBs havingthe same VRB number may be mapped into the PRBs having different PRBnumbers at the first slot and the second slot. Two PRBs, which arerespectively located at two slots of the subframe and have the same VRBnumber, will be referred to as a pair of VRBs.

FIG. 3 illustrates a downlink (DL) subframe structure used in 3GPPLTE/LTE-A.

Referring to FIG. 3, a DL subframe is divided into a control region anda data region. A maximum of three (four) OFDM symbols located in a frontportion of a first slot within a subframe correspond to the controlregion to which a control channel is allocated. A resource regionavailable for PDCCH transmission in the DL subframe is referred to as aPDCCH region hereinafter. The remaining OFDM symbols correspond to thedata region to which a physical downlink shared chancel (PDSCH) isallocated. A resource region available for PDSCH transmission in the DLsubframe is referred to as a PDSCH region hereinafter. Examples ofdownlink control channels used in 3GPP LTE include a physical controlformat indicator channel (PCFCH), a physical downlink control channel(PDCCH), a physical hybrid ARQ indicator channel (PHICH), etc. ThePCFICH is transmitted at a first OFDM symbol of a subframe and carriesinformation regarding the number of OFDM symbols used for transmissionof control channels within the subframe. The PHICH is a response ofuplink transmission and carries an HARQ acknowledgment (ACK)/negativeacknowledgment (NACK) signal.

Control information carried on the PDCCH is called downlink controlinformation (DCI). The DCI contains resource allocation information andcontrol information for a UE or a UE group. For example, the DCIincludes a transport format and resource allocation information of adownlink shared channel (DL-SCH), a transport format and resourceallocation information of an uplink shared channel (UL-SCH), paginginformation of a paging channel (PCH), system information on the DL-SCH,information about resource allocation of an upper layer control messagesuch as a random access response transmitted on the PDSCH, a transmitcontrol command set with respect to individual UEs in a UE group, atransmit power control command, information on activation of a voiceover IP (VoIP), downlink assignment index (DAI), etc. The transportformat and resource allocation information of the DL-SCH are also calledDL scheduling information or a DL grant and the transport format andresource allocation information of the UL-SCH are also called ULscheduling information or a UL grant. The size and purpose of DCIcarried on a PDCCH depend on DCI format and the size thereof may bevaried according to coding rate. Various formats, for example, formats 0and 4 for uplink and formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 3 and 3Afor downlink, have been defined in 3GPP LTE. Control information such asa hopping flag, information on RB allocation, modulation coding scheme(MCS), redundancy version (RV), new data indicator (NDI), information ontransmit power control (TPC), cyclic shift demodulation reference signal(DMRS), UL index, channel quality information (CQI) request, DLassignment index, HARQ process number, transmitted precoding matrixindicator (TPMI), precoding matrix indicator (PMI), etc. is selected andcombined based on DCI format and transmitted to a UE as DCI.

In general, a DCI format for a UE depends on transmission mode (TM) setfor the UE. In other words, only a DCI format corresponding to aspecific TM can be used for a UE configured in the specific TM.

A PDCCH is transmitted on an aggregation of one or several consecutivecontrol channel elements (CCEs). The CCE is a logical allocation unitused to provide the PDCCH with a coding rate based on a state of a radiochannel The CCE corresponds to a plurality of resource element groups(REGs). For example, a CCE corresponds to 9 REGs and an REG correspondsto 4 REs. 3GPP LTE defines a CCE set in which a PDCCH can be located foreach UE. A CCE set from which a UE can detect a PDCCH thereof is calleda PDCCH search space, simply, search space. An individual resourcethrough which the PDCCH can be transmitted within the search space iscalled a PDCCH candidate. A set of PDCCH candidates to be monitored bythe UE is defined as the search space. In 3GPP LTE/LTE-A, search spacesfor DCI formats may have different sizes and include a dedicated searchspace and a common search space. The dedicated search space is aUE-specific search space and is configured for each UE. The commonsearch space is configured for a plurality of UEs. Aggregation levelsdefining the search space is as follows.

TABLE 3 Number of Search Space PDCCH Aggregation Level candidates Type LSize [in CCEs] M^((L)) UE-specific 1 6 6 2 12 6 4 8 2 8 16 2 Common 4 164 8 16 2

A PDCCH candidate corresponds to 1, 2, 4 or 8 CCEs according to CCEaggregation level. An eNB transmits a PDCCH (DCI) on an arbitrary PDCCHcandidate with in a search space and a UE monitors the search space todetect the PDCCH (DCI). Here, monitoring refers to attempting to decodeeach PDCCH in the corresponding search space according to all monitoredDCI formats. The UE can detect the PDCCH thereof by monitoring pluralPDCCHs. Since the UE does not know the position in which the PDCCHthereof is transmitted, the UE attempts to decode all PDCCHs of thecorresponding DCI format for each subframe until a PDCCH having the IDthereof is detected. This process is called blind detection (or blinddecoding (BD)).

The eNB can transmit data for a UE or a UE group through the dataregion. Data transmitted through the data region may be called userdata. For transmission of the user data, a physical downlink sharedchannel (PDSCH) may be allocated to the data region. A paging channel(PCH) and downlink-shared channel (DL-SCH) are transmitted through thePDSCH. The UE can read data transmitted through the PDSCH by decodingcontrol information transmitted through a PDCCH. Informationrepresenting a UE or a UE group to which data on the PDSCH istransmitted, how the UE or UE group receives and decodes the PDSCH data,etc. is included in the PDCCH and transmitted. For example, if aspecific PDCCH is CRC (cyclic redundancy check)-masked having radionetwork temporary identify (RNTI) of “A” and information about datatransmitted using a radio resource (e.g., frequency position) of “B” andtransmission format information (e.g., transport block size, modulationscheme, coding information, etc.) of “C” is transmitted through aspecific DL subframe, the UE monitors PDCCHs using RNTI information anda UE having the RNTI of “A” detects a PDCCH and receives a PDSCHindicated by “B” and “C” using information about the PDCCH.

A reference signal (RS) to be compared with a data signal is necessaryfor the UE to demodulate a signal received from the eNB. A referencesignal refers to a predetermined signal having a specific waveform,which is transmitted from the eNB to the UE or from the UE to the eNBand known to both the eNB and UE. The reference signal is also called apilot. Reference signals are categorized into a cell-specific RS sharedby all UEs in a cell and a modulation RS (DM RS) dedicated for aspecific UE. A DM RS transmitted by the eNB for demodulation of downlinkdata for a specific UE is called a UE-specific RS. Both or one of DM RSand CRS may be transmitted on downlink. When only the DM RS istransmitted without CRS, an RS for channel measurement needs to beadditionally provided because the DM RS transmitted using the sameprecoder as used for data can be used for demodulation only. Forexample, in 3GPP LTE(-A), CSI-RS corresponding to an additional RS formeasurement is transmitted to the UE such that the UE can measurechannel state information. CSI-RS is transmitted in each transmissionperiod corresponding to a plurality of subframes based on the fact thatchannel state variation with time is not large, unlike CRS transmittedper subframe.

FIG. 4 illustrates an exemplary uplink subframe structure used in 3GPPLTE/LTE-A.

Referring to FIG. 4, a UL subframe can be divided into a control regionand a data region in the frequency domain. One or more PUCCHs (physicaluplink control channels) can be allocated to the control region to carryuplink control information (UCI). One or more PUSCHs (Physical uplinkshared channels) may be allocated to the data region of the UL subframeto carry user data.

In the UL subframe, subcarriers spaced apart from a DC subcarrier areused as the control region. In other words, subcarriers corresponding toboth ends of a UL transmission bandwidth are assigned to UCItransmission. The DC subcarrier is a component remaining unused forsignal transmission and is mapped to the carrier frequency f0 duringfrequency up-conversion. A PUCCH for a UE is allocated to an RB pairbelonging to resources operating at a carrier frequency and RBsbelonging to the RB pair occupy different subcarriers in two slots.Assignment of the PUCCH in this manner is represented as frequencyhopping of an RB pair allocated to the PUCCH at a slot boundary. Whenfrequency hopping is not applied, the RB pair occupies the samesubcarrier.

The PUCCH can be used to transmit the following control information.

-   -   Scheduling Request (SR): This is information used to request a        UL-SCH resource and is transmitted using On-Off Keying (OOK)        scheme.    -   HARQ ACK/NACK: This is a response signal to a downlink data        packet on a PDSCH and indicates whether the downlink data packet        has been successfully received. A 1-bit ACK/NACK signal is        transmitted as a response to a single downlink codeword and a        2-bit ACK/NACK signal is transmitted as a response to two        downlink codewords. HARQ-ACK responses include positive ACK        (ACK), negative ACK (NACK), discontinuous transmission (DTX) and        NACK/DTX. Here, the term HARQ-ACK is used interchangeably with        the term HARQ ACK/NACK and ACK/NACK.    -   Channel State Indicator (CSI): This is feedback information        about a downlink channel Feedback information regarding MIMO        includes a rank indicator (RI) and a precoding matrix indicator        (PMI).

The quantity of control information (UCI) that a UE can transmit througha subframe depends on the number of SC-FDMA symbols available forcontrol information transmission. The SC-FDMA symbols available forcontrol information transmission correspond to SC-FDMA symbols otherthan SC-FDMA symbols of the subframe, which are used for referencesignal transmission. In the case of a subframe in which a soundingreference signal (SRS) is configured, the last SC-FDMA symbol of thesubframe is excluded from the SC-FDMA symbols available for controlinformation transmission. A reference signal is used to detect coherenceof the PUCCH. The PUCCH supports various formats according toinformation transmitted thereon.

Table 4 shows the mapping relationship between PUCCH formats and UCI inLTE/LTE-A.

TABLE 4 Number of bits per PUCCH Modulation subframe, format schemeM_(bit) Usage Etc. 1 N/A N/A SR (Scheduling Request) 1a BPSK 1 ACK/NACKor One codeword SR + ACK/NACK 1b QPSK 2 ACK/NACK or Two codeword SR +ACK/NACK 2 QPSK 20 CQI/PMI/RI Joint coding ACK/NACK (extended CP) 2aQPSK + BPSK 21 CQI/PMI/RI + Normal CP ACK/NACK only 2b QPSK + QPSK 22CQI/PMI/RI + Normal CP ACK/NACK only 3 QPSK 48 ACK/NACK or SR + ACK/NACKor CQI/PMI/RI + ACK/NACK

Referring to Table 4, PUCCH formats 1/1a/1b are used to transmitACK/NACK information, PUCCH format 2/2a/2b are used to carry CSI such asCQI/PMI/RI and PUCCH format 3 is used to transmit ACK/NACK information.

Generally, in a cellular communication system, various methods foracquiring position information of a UE in a network are used.Representatively, a positioning scheme based on OTDOA (observed timedifference of arrival) exists in the LTE system. According to thepositioning scheme, the UE may be configured to receive PRS (positioningreference signal) transmission related information of eNBs from a higherlayer signal, and may transmit a reference signal time difference (RSTD)which is a difference between a reception time of a PRS transmitted froma reference eNB and a reception time of a PRS transmitted from aneighboring eNB to a eNB or network by measuring PRS transmitted fromcells in the periphery of the UE, and the network calculates a positionof the UE by using RSTD and other information. In addition, otherschemes such as an A-GNSS(Assisted Global Navigation Satellite System)positioning scheme, an E-CID(Enhanced Cell-ID) scheme, and aUTDOA(Uplink Time Difference of Arrival) exist, and variouslocation-based services (for example, advertisements, position tracking,emergency communication means, etc.) may be used based on thesepositioning schemes.

[LTE Positioning Protocol]

In the LTE system, an LPP (LTE positioning protocol) has been defined tothe OTDOA scheme, and notifies the UE of OTDOA-ProvideAssistanceDatahaving the following configuration through IE (information element).

  -- ASN1START   OTDOA-ProvideAssistanceData ::= SEQUENCE {  otdoa-ReferenceCellInfoOTDOA-ReferenceCellInfo OPTIONAL, -- Need ON  otdoa-NeighbourCellInfo  OTDOA-NeighbourCellInfoList OPTIONAL, -- NeedON   otdoa-Error OTDOA-Error OPTIONAL, -- Need ON   ...   } -- ASN1STOP

In this case, OTDOA-ReferenceCellInfo means a cell which is a referenceof RSTD measurement, and is configured as follows.

  -- ASN1START   OTDOA-ReferenceCellInfo ::= SEQUENCE {   physCellIdINTEGER (0..503),   cellGlobalId ECGI OPTIONAL, -- Need ON   earfcnRefARFCN-ValueEUTRA OPTIONAL, --Cond NotSameAsServ0   antennaPortConfigENUMERATED {ports1-or-2, ports4, ... }   OPTIONAL, -- CondNotSameAsServ1   cpLength ENUMERATED { normal, extended, ... },  prsInfo PRS-Info OPTIONAL, -- Cond PRS   ...,   [[ earfcnRef-v9a0ARFCN-ValueEUTRA-v9a0 OPTIONAL -- Cond NotSameAsServ2   ]]   }   --ASN1STOP

Meanwhile, OTDOA-NeighbourCellInfo means cells (for example, eNB or TP)which is a target for RSTD measurement, and may include information onmaximum 24 neighboring cells per frequency layer with respect to maximumthree frequency layers. That is, OTDOA-NeighbourCellInfo may notify theUE of information on a total of 3*24=72 cells.

  -- ASN1START   OTDOA-NeighbourCellInfoList  ::=  SEQUENCE  (SIZE(1..maxFreqLayers)) OF OTDOA-NeighbourFreqInfo   OTDOA-NeighbourFreqInfo::= SEQUENCE (SIZE (1..24)) OF OTDOA-NeighbourCellInfoElement  OTDOA-NeighbourCellInfoElement ::= SEQUENCE {   physCellId INTEGER(0..503),   cellGlobalId ECGI OPTIONAL, -- Need ON  earfcn ARFCN-ValueEUTRA OPTIONAL,  --  Cond NotSameAsRef0   cpLengthENUMERATED {normal, extended, ...}   OPTIONAL, -- Cond NotSameAsRef1  prsInfo PRS-Info OPTIONAL, -- Cond NotSameAsRef2   antennaPortConfigENUMERATED {ports-1-or-2, ports-4, ...}   OPTIONAL, -- CondNotsameAsRef3   slotNumberOffset INTEGER (0..19) OPTIONAL, -- CondNotSameAsRef4   prs-SubframeOffset INTEGER (0..1279) OPTIONAL,  -- CondInterFreq   expectedRSTD INTEGER (0..16383),  expectedRSTD-Uncertainty  INTEGER (0..1023),   ...,   [[ earfcn-v9a0ARFCN-ValueEUTRA-v9a0  OPTIONAL -- Cond NotSameAsRef5   ]]   }  maxFreqLayers INTEGER ::= 3   -- ASN1STOP

In this case, PRS-Info which is IE included in OTDOA-ReferenceCellInfoand OTDOA-NeighbourCellInfo has PRS information, and is specificallyconfigured, as follows, as PRS Bandwidth, PRS Configuration Index(IPRS), Number of Consecutive Downlink Subframes, and PRS MutingInformation.

PRS-Info ::= SEQUENCE { prs-Bandwidth ENUMERATED { n6, n15, n25, n50,n75, n100, ... }, prs-ConfigurationIndex INTEGER (0..4095), numDL-FramesENUMERATED {sf-1, sf-2, sf-4, sf-6, ...}, ..., prs-MutingInfo-r9  CHOICE{ po2-r9   BIT STRING (SIZE(2)), po4-r9   BIT STRING (SIZE(4)),po8-r9   BIT STRING (SIZE(8)), po16-r9 BIT STRING (SIZE(16)), ... }OPTIONAL    -- Need OP } -- ASN1STOP

FIG. 5 illustrates a PRS transmission structure according to the aboveparameters.

At this time, PRS Periodicity and PRS Subframe Offset are determined inaccordance with a value of PRS Configuration Index (IPRS), and theircorrelation is as follows.

TABLE 5 PRS Configuration Index PRS Periodicity PRS Subframe Offset(I_(PRS)) (subframes) (subframes)  0-159 160 I_(PRS) 160-479 320I_(PRS)-160  480-1119 640 I_(PRS)-480  1120-23399 1280  I_(PRS)-1120

[PRS(Positioning Reference Signal)]

The PRS has a transmission occasion, that is, a positioning occasion ata period of 160, 320, 640, or 1280 ms, and may be transmitted for N DLsubframes consecutive for the positioning occasion. In this case, N mayhave a value of 1, 2, 4 or 6. Although the PRS may be transmittedsubstantially at the positioning occasion, the PRS may be muted forinter-cell interference control cooperation. Information on such PRSmuting is signaled to the UE as prs-MutingInfo. A transmission bandwidthof the PRS may be configured independently unlike a system bandwidth ofa serving eNB, and is transmitted to a frequency band of 6, 15, 25, 50,75 or 100 resource blocks (RBs). Transmission sequences of the PRS aregenerated by initializing a pseudo-random sequence generator for everyOFDM symbol using a function of a slot index, an OFDM symbol index, acyclic prefix (CP) type, and a cell ID. The generated transmissionsequences of the PRS are mapped to resource elements (REs) depending ona normal CP or an extended CP as shown in FIG. 6 (normal CP) and FIG. 7(extended CP). A position of the mapped REs may be shifted on thefrequency axis, and a shift value is determined by a cell ID. Thepositions of the REs for transmission of the PRS shown in FIGS. 6 and 7correspond to the case that the frequency shift is 0.

The UE receives designated configuration information on a list of PRSsto be searched from a position management server of a network to measurePRSs. The corresponding information includes PRS configurationinformation of a reference cell and PRS configuration information ofneighboring cells. The configuration information of each PRS includes ageneration cycle and offset of a positioning occasion, and the number ofcontinuous DL subframes constituting one positioning occasion, cell IDused for generation of PRS sequences, a CP type, the number of CRSantenna ports considered at the time of PRS mapping, etc. In addition,the PRS configuration information of the neighboring cells includes aslot offset and a subframe offset of the neighboring cells and thereference cell, an expected RSTD, and a level of uncertainty of theexpected RSTD to support determination of the UE when the UE determinesa timing point and a level of time window used to search for the PRS todetect the PRS transmitted from the neighboring cell.

Meanwhile, the RSTD refers to a relative timing difference between anadjacent or neighboring cell j and a reference cell i. In other words,the RSTD may be expressed by T_(subframeRxj)−T_(subframeRxi), whereinT_(subframeRxj) refers to a timing point at which a UE starts to receivea specific subframe from the neighboring cell j, and T_(subframeRxi)refers to a timing point at which a UE starts to receive a subframe,which is closest to the specific subframe received from the neighboringcell j in terms of time and corresponds to the specific subframe, fromthe reference cell i. A reference point for an observed subframe timedifference is an antenna connector of the UE.

Although the aforementioned positioning schemes of the related art arealready supported by the 3GPP UTRA and E-UTRAN standard (for example,(LTE Rel-9), higher accuracy is recently required for an in-buildingpositioning scheme. That is, although the positioning schemes of therelated art may commonly be applied to outdoor/indoor environments, incase of E-CID scheme, general positioning accuracy is known as 150 m ina non-LOS (NLOS) environment and as 50 m in a LOS environment. Also, theOTDOA scheme based on the PRS has a limit in a positioning error, whichmay exceed 100 m, due to an eNB synchronization error, a multipathpropagation error, a quantization error in RSTD measurement of a UE, anda timing offset estimation error. Also, since a GNSS receiver isrequired in case of the A-GNSS scheme, the A-GNSS scheme has a limit incomplexity and battery consumption, and has a restriction in usingin-building positioning.

[LTE (LTE-U) in Unlicensed Band]

Recently, with the advent of a smart device, data traffic isconsiderably increasing. As a result, a next generation wirelesscommunication system such as 3GPP LTE-A is trying to find ways toefficiently utilizing a limited frequency band. In particular, the nextgeneration wireless communication system considers managing a cellularnetwork on such an unlicensed band as 2.4 GHz or 5 GHz. The unlicensedband regulates each of communication nodes to perform wirelesstransmission and reception based on an LBT operation such as CCA (clearchannel assessment) and the like.

For example, regulation of Europe illustrates two types of LBT-basedchannel access operation respectively referred to as FBE (frame basedequipment) and LBE (load based equipment). The FBE configures a singleframe using channel occupancy time (e.g., 1-10 ms) corresponding to timecapable of maintaining transmission when a communication node succeedsin accessing a channel and idle time corresponding to the minimum 5% ofthe channel occupancy time. The CCA is defined as an operation ofobserving a channel for at least 20 μs of the last part of the idletime. In this case, a communication node periodically performs the CCAin a unit of the frame. If a channel is unoccupied, the communicationnode transmits data during the channel occupancy time. If a channel isoccupied, the communication node waits until a CCA slot of a next periodwhile postponing transmission. FIG. 8 shows an example of the FBEoperation.

Meanwhile, in case of the LBE, a communication node configures a valueof q∈{4, 5, . . . , 32} first and performs CCA on a single slot. If achannel is unoccupied in the first CCA slot, the communication node cantransmit data by securing channel occupancy time as much as a length of(13/32)q ms. If a channel is occupied in the first CCA slot, thecommunication node randomly selects a value of N∈{1, 2, . . . , q},stores the selected value as an initial value of a counter, and senses achannel state in a unit of a CCA slot. If a channel is unoccupied in aspecific CCA slot, the communication node reduces the value stored inthe counter by 1. If the value stored in the counter becomes 0, a userequipment (UE) can transmit data with channel occupancy time as much asa length of (13/32)q ms. FIG. 9 shows an example of the LBE operation.

In the example, an occupied state of a channel or an unoccupied state ofthe channel can be determined based on whether or not reception powerexceeds a prescribed threshold in a CCA slot. For example, according tothe Wi-Fi standard (e.g., 801.11ac), a CCA threshold is regulated by −62dBm and −82 dBm for a non-Wi-Fi signal and a Wi-Fi signal, respectively.In particular, if a signal rather than a Wi-Fi signal is received withpower equal to or greater than −62 dBm, an STA (station) or an AP(access point) does not perform signal transmission to avoidinterference occurrence. Meanwhile, a wireless communication system suchas 3GPP LTE-A, and the like, considers a method of combining a celloperating on a licensed band (hereinafter, L-cell) and a cell operatingon an unlicensed band (hereinafter, U-cell) with each other using a CA(carrier aggregation) technique and a method of performing LBT-basedDL/UL transmission in the U-cell.

Meanwhile, although the aforementioned legacy positioning schemes arealready supported by 3GPP UTRA and E-UTRA standard (e.g., LTE Rel-9), itis necessary to have an enhanced positioning scheme to have a higheraccuracy for in-building positioning. In particular, although the legacypositioning schemes correspond to techniques capable of being commonlyapplied to outdoor/indoor environment, in case of E-CID scheme, ageneral positioning accuracy is known as 150 m and 50 m in NLOSenvironment and LOS environment, respectively. Moreover, the OTDOAscheme based on a PRS has such a critical point as a positioning errorcapable of exceeding 100 m due to an eNB synchronization error, an errorgenerated by multipath propagation, an RSTD measurement quantizationerror of a UE, timing offset estimation error, and the like. In case ofA-GNSS scheme, since the A-GNSS scheme requires a GNSS receiver, thisscheme has a critical point in complexity and battery consumption. Thisscheme has a restriction on in-building positioning.

The present invention basically considers a method for an eNB tocalculate location information of a UE. In particular, if a cellularnetwork transmits a specific pilot signal (e.g., a specific referencesignal capable of being separately identified according to an eNB/TP(transmission point)) to a UE, the UE measures each pilot signal,calculates a positioning-related estimation value using a specificpositioning scheme (e.g., OTDOA and RSTD estimation value report), andreports the estimation value to the eNB. And, the present inventionconsiders a situation that L-Cell operating on a legacy licensed band iscombined with U-cell operating on an unlicensed band.

In case of transmitting a PRS using a wider bandwidth, it may be able toincrease RSTD measurement accuracy of a UE due to duality of frequencydomain and time domain. This is because, since a resolution of the timedomain is equivalent to inverse of the frequency domain, if a signal istransmitted on a wider frequency band, a unit of time capable of beingmeasured by the UE becomes more detail. Hence, it may be able toaggregate an unlicensed band of a wider bandwidth together in the samecell using CA technique to transmit a PRS. If a UE is able to utilizethe PRS, it is expected that it is able to estimate RSTD of higherresolution. Or, although a PRS is not transmitted using both a licensedband and an unlicensed band at the same time, if a PRS isopportunistically transmitted on an unlicensed band of a relativelywider frequency unit (wider bandwidth) and a UE is able to utilize thePRS, it is expected that it is able to increase measurement accuracy ofthe UE.

In case of considering environment that wireless transmission andreception are performed based on an LBT operation on an unlicensed band,when a PRS is transmitted, it may be difficult for a UE to measure thePRS. Since the UE is unable to precisely know channel occupancy time ofeach of neighboring eNBs, it is difficult for the UE to identify timingat which a PRS of a neighboring eNB is transmitted. Since it is unableto guarantee that channel occupancy time of each eNB is aligned, if aneNB transmits a signal such as data at the timing that a specific eNBtransmits a PRS, the signal may work as big interference. When a UEintends to measure a value such as RSTD by utilizing PRSs transmittedfrom two eNBs, if one of the eNBs has no DL data to transmit and doesnot occupy channel occupancy time, the UE is unable to measure the valueor the UE may obtain an outdated measurement value because the UEperforms measurement after waiting for a channel occupancy time of theeNB. Due to the aforementioned various reasons, when eNBs transmit PRSson an unlicensed band and a UE intends to utilize the PRSs, it may benecessary for the eNBs to transmit the PRSs via coordination.

And, it may be able to configure at least one or more subframes (orpositioning occasions) in which a PRS is transmitted on an unlicensedband to be overlapped via a predefined coordination or coordination ofeNBs via a signal between the eNBs.

FIG. 10 shows an example of configuring a subframe (or positioningoccasion) in which the PRS is transmitted. A case 1 and a case 2 of FIG.10 illustrate a case that a PRS transmission subframe (or positioningoccasion) has a period/offset for a subframe of absolute timingirrespective of a channel occupancy time configuration. A case 3illustrates a case that a PRS transmission subframe (or positioningoccasion) is indicated by a specific subframe period belonging to achannel occupancy time period.

Meanwhile, in case of the cases 2 and 3 of FIG. 10, an eNB 2 transmits aPRS in an SF #n, whereas eNBs 1 and 3 do not transmit a PRS. Hence, in asituation that a PRS is transmitted on an unlicensed band and a UEmeasure the PRS, the UE performs positioning-related measurement on aserving cell only when a PRS transmission subframe of the serving cellbelongs to channel occupancy time. On the contrary, since the UE isunable to identify channel occupancy time for the remaining adjacentcell, the UE performs blind detection on a PRS of the adjacent cellwithin the channel occupancy time to which the PRS transmission subframeof the serving cell is set to perform the positioning-relatedmeasurement.

In case of the case 3, although the eNBs 1 and 3 transmit a PRS in an SF#n+4, data rather than a PRS can be transmitted in the eNB2. In thiscase, the data transmitted from the eNB2 may work as an interferencesource for PRS measurement of a different eNB.

In order to avoid the interference, it may be able to configure not totransmit data in a subframe in which a PRS is not transmitted withinchannel occupation time including a PRS transmission subframe via apredefined coordination or a coordination of eNBs via a signal betweenthe eNBs. In particular, it may be able to configure a muting operationto be performed in the subframe in which the PRS is not transmitted.

Or, it may be able to configure specific channel occupancy time to beused for transmitting a PRS only via a predefined coordination or acoordination of eNBs via a signal between the eNBs. And, it may be ableto configure all subframes (or certain number of subframes) within thechannel occupancy time to transmit a PRS.

Similarly, if at least one or more PRS transmission subframes areincluded in specific channel occupancy time, it may be able to configureall subframes (or certain number of subframes) within the channeloccupancy time to transmit a PRS.

Whether to include a PRS transmission subframe in specific channeloccupancy time can be commonly configured via a predefined coordinationor a coordination of eNBs via a signal between the eNBs. And,information on whether or not a PRS transmission subframe is included inspecific channel occupancy time can be indicated to a UE. In this case,a length of the channel occupancy time in which the PRS transmissionsubframe is included can be identically configured between eNBs.

Information on whether or not a PRS transmission subframe is included inspecific channel occupancy time can be indicated using a methoddescribed in the following.

-   -   Whether or not a PRS transmission subframe is included in        channel occupancy timing corresponding to specific timing is        indicated via a higher layer signal. For example, if an SF #n,        an SF #n+40, and an SF #n+80 are indicated by a higher layer        signal and channel occupancy time is configured by {SF #n+15˜SF        #n+25} and {SF #n+35˜SF #n+45}, a UE may consider that channel        occupancy time corresponding to {SF #n+35˜SF #n+45} includes a        PRS transmission subframe only. As a different example, if a        period/offset of a PRS is indicated and a subframe corresponding        to the period/offset is included in channel occupancy time, a UE        may consider that a PRS transmission subframe is included in the        channel occupancy time.    -   Whether or not a PRS transmission subframe is included in        channel occupancy timing corresponding to specific timing is        indicated via DCI of L-Cell.    -   Whether or not a PRS transmission subframe is included in        channel occupancy timing corresponding to specific timing is        indicated via DCI of U-Cell.    -   If an eNB practically transmits data in accordance with a        subframe or an OFDM symbol boundary of LTE-A system, a timing        gap may exist between idle determination timing of U-Cell and        actual transmission timing. In particular, since the eNB and a        UE are unable to exclusively use the U-Cell and the U-Cell is        used via CS-based contention, a different system may attempt to        transmit information during the timing gap. Hence, for example,        the U-Cell may transmit a reservation signal during the timing        gap to prevent the different system from transmitting        information during the timing gap. In this case, the reservation        signal may correspond to “dummy information” or “copy for a part        of PDSCH” which is transmitted to reserve the U-Cell as a        resource of the UCell. The reservation signal can be transmitted        during the timing gap (i.e., between idle determination timing        of U-Cell and actual transmission timing). Whether or not a PRS        transmission subframe is included in channel occupation time        corresponding to specific timing is indicated through the        reservation signal.

A UE performs PRS blind detection on a reference cell and a neighborcell in a time period indicated (predetermined) as channel occupancytime in which a PRS transmission subframe is included to performpositioning-related measurement.

According to current LTE standard, a transmission sequence of a PRS isgenerated by initializing a pseudo-random sequence generator in everyOFDM symbol with a function of a slot index, an OFDM symbol index, acyclic prefix (CP) type, and a physical cell ID. As shown in FIGS. 6 and7, the generated sequences are mapped to a resource element (RE)depending on a normal CP or an extended CP according to the reference.

REFERENCE

The reference signal sequence R_(L,N) _(S) (m) shall be mapped tocomplex-valued modulation symbols a_(k,l) ^((p)) used as referencesignal for antenna port p=6 in slot n_(s).

$\begin{matrix}{{a_{k,l}^{(p)} = {{r_{l,n_{s}}\left( m^{\prime} \right)}\mspace{14mu} {where}}}{{Normal}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}\text{:}}{k = {{6\left( {m + N_{RB}^{DL} - N_{R\; B}^{PRS}} \right)} + {\left( {6 - l + v_{shift}} \right){mod}\mspace{11mu} 6}}}{l = \left\{ {{{\begin{matrix}{3,5,6} & {{{if}\mspace{14mu} n_{s}{mod}\mspace{14mu} 2} = 0} \\{1,2,3,5,6} & \begin{matrix}{{{{if}\mspace{14mu} n_{s}{mod}\mspace{14mu} 2} = {1\mspace{20mu} {and}}}\mspace{14mu}} \\\left( {1\mspace{11mu} {or}\mspace{11mu} 2\mspace{11mu} {PBCH}\mspace{14mu} {antenna}\mspace{14mu} {ports}} \right)\end{matrix} \\{2,3,5,6} & \begin{matrix}{{{{if}\mspace{14mu} n_{s}{mod}\mspace{14mu} 2} = {1\mspace{20mu} {and}}}\mspace{14mu}} \\\left( {4\mspace{11mu} {PBCH}\mspace{14mu} {antenna}\mspace{14mu} {ports}} \right)\end{matrix}\end{matrix}m} = 0},1,\ldots \;,{{{2 \cdot N_{RB}^{PRS}} - {1m^{\prime}}} = {{m + N_{RB}^{\max,{DL}} - {N_{RB}^{PRS}{Extended}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}\text{:}k}} = {{{6\left( {m + N_{RB}^{DL} - N_{R\; B}^{PRS}} \right)} + {\left( {5 - l + v_{shift}} \right){mod}\mspace{11mu} 6l}} = \left\{ {{{\begin{matrix}{4,5} & {{{if}\mspace{14mu} n_{s}{mod}\mspace{14mu} 2} = 0} \\{1,2,4,5} & \begin{matrix}{{{{if}\mspace{14mu} n_{s}{mod}\mspace{14mu} 2} = {1\mspace{20mu} {and}}}\mspace{14mu}} \\\left( {1\mspace{11mu} {or}\mspace{11mu} 2\mspace{11mu} {PBCH}\mspace{14mu} {antenna}\mspace{14mu} {ports}} \right)\end{matrix} \\{2,4,5} & \begin{matrix}{{{{if}\mspace{14mu} n_{s}{mod}\mspace{14mu} 2} = {1\mspace{20mu} {and}}}\mspace{14mu}} \\\left( {4\mspace{11mu} {PBCH}\mspace{14mu} {antenna}\mspace{14mu} {ports}} \right)\end{matrix}\end{matrix}m} = 0},1,\ldots \;,{{{2 \cdot N_{RB}^{PRS}} - {1m^{\prime}}} = {m + N_{RB}^{\max,{DL}} - N_{RB}^{PRS}}}} \right.}}}} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

According to LTE standard, a PRS is not mapped to an RE to which PBCH,PSS, or SSS is assigned. And, the PRS is not mapped to an OFDM symbol inwhich a CRS is transmitted. In order to avoid a collision with a PDCCHregion, the PRS is not mapped to first three OFDM symbols.

Due to the characteristic of an unlicensed band, when a signal is nottransmitted during prescribed time, if a neighboring eNB performs CCA, achannels state can be determined as idle and it may attempt to performcommunication on the unlicensed band via channel occupancy time periodconfiguration. Hence, if a signal is not transmitted in a specific OFDMsymbol of a subframe in which a PRS is transmitted, it mayunintentionally recognize that the neighboring eNB is in an idle state.

Hence, PRS RE mapping of a subframe in which a PRS is transmitted on anunlicensed band can be configured according to rules described in thefollowing.

-   -   It may be able to configure a specific subframe not to transmit        PDCCH on an unlicensed band. When a subframe in which a PRS is        transmitted is configured not to transmit PDCCH on an unlicensed        band, if the number of PBCH antenna port corresponds to 1 or 2,        the PRS can be mapped to a specific RE of second and third OFDM        symbols (l=1,2) of a first slot. In case of a subframe in which        a PRS is transmitted on an unlicensed band, if the number of        PBCH antenna port corresponds to 4, the PRS can be mapped to a        specific RE of third OFDM symbol (l=2) of a first slot.    -   It may be able to configure a specific subframe not to transmit        PDCCH and a CRS on an unlicensed band. In this case, a PRS RE        can be mapped to a specific RE of an OFDM symbol including an RE        to which a CRS is supposed to be transmitted. And, if a specific        subframe is configured not to transmit a CRS on an unlicensed        band, it may be able to configure a PRS to be mapped to a        specific RE of a specific PFDM symbol I=1 for 1 or 2 CRS antenna        port, I=2 for 2 or 4 CRS antenna ports).    -   It may be able to configure not to transmit PBCH, PSS, and/or        SSS due to aperiodic/opportunistic transmission on an unlicensed        band. In this case, a PRS RE can be mapped to a specific RE of        an OFDM symbol including an RE to which PBCH, PSS, and/or SSS        are supposed to be transmitted.

It may be able to configure not to transmit a CRS and PDCCH to a PRStransmission subframe belonging to specific channel occupation time ofan unlicensed band.

If PBCH, PSS, and SSS are collided with PRS transmission in a specificsubframe belonging to specific channel occupancy time of an unlicensedband, it may be able to configure the PRS transmission to bepreferentially performed. Or, it may be able to configure the PBCH, PSS,and SSS transmission to be preferentially performed. The configurationcan be configured in advance or can be signaled to a UE.

When an eNB performs CCA on an unlicensed band and identifies a channelstate, if the eNB performs the CCA at a time on a wider frequency band,although a partial band is occupied by other devices, the eNB maydetermine that the whole band is busy. Due to the operation, anoccupation probability is relatively reduced on the unlicensed band anddata is inefficiently transmitted. In order to avoid the inefficientsituation, the whole frequency band is divided into relatively narrowfrequency bands and CCA can be independently performed on each of thefrequency bands. In this case, CCA is performed on each of the frequencybands and it may be able to independently configure channel occupancytime. FIG. 11 shows an example that an unlicensed band of 80 MHz isdivided into four 20 MHz bands, CCA is performed on each of the four 20MHz bands, and channel occupancy time is configured.

Whether or not an eNB commonly includes a PRS transmission subframe inspecific channel occupancy time for prescribed time duration can beindependently configured for each frequency band via a predefinedcoordination or a coordination of eNBs via a signal between the eNBs.

Or, it may be able to eNB-commonly configure a PRS transmission subframeto be always included in channel occupation time for a specificfrequency band for a prescribed time period via a predefinedcoordination or a coordination of eNBs via a signal between the eNBs.

Or, it may be able to eNB-commonly configure a PRS transmission subframeto be included in a partial channel occupation time for a specificfrequency band for a prescribed time period via a predefinedcoordination or a coordination of eNBs via a signal between the eNBs.

Meanwhile, according to current LTE standard, a position of an RE towhich a PRS is mapped can be shifted on a frequency axis. In this case,a shift value is determined by a physical cell ID. Specifically, since aposition of an RE to which a PRS is mapped is determined by a value of(PCID mod 6), if a plurality of eNBs transmit a PRS at the same time,the number of eNBs transmitting a PRS to the same RE increases in somecases and an interference problem may occur. As a result, an accuracy ofpositioning-related measurement can be reduced. In order to solve theproblem, it may be able to configure channel occupancy time to which aPRS transmission subframe belongs to be overlapped between eNBs nottransmitting a PRS to the same RE via a predefined coordination or acoordination of eNBs via a signal between the eNBs. Hence, a UE performsblind detection while expecting that a PRS is transmitted in channeloccupancy time of eNBs not transmitting the PRS to the same RE on theunlicensed band and performs positioning-related measurement.

For example, when a neighboring eNB has PCID 0 to 11, it may be able toconfigure a PRS transmission subframe shown in FIG. 12. Specifically, itmay be able to configure an eNB having PCID 0 to 5 to have channeloccupancy time to which a PRS transmission subframe belongs during acommon time period and configure an eNB having PCID 6 to 11 to havechannel occupancy time to which a PRS transmission subframe belongsduring a different common time period.

In the aforementioned proposals, an eNB becoming a target ofcoordination can be determined by a location server. Or, whether or notan individual eNB is coordinated can be determined using such a schemeas request and respond in a manner of being triggered by a request of aspecific eNB. And, a coordination range can also be indicated by thelocation server (or, a specific eNB triggering coordination). Forexample, the location server (or, a specific eNB triggeringcoordination) may indicate that positioning-related coordination on theunlicensed band is valid for a specific frequency/time resource rangeonly.

A UE can independently report a positioning-related measurement value onan unlicensed band and a positioning-related measurement value on alicensed band. For example, the UE can report RSTD and RSTD quality foran unlicensed band and a licensed band, respectively.

It may inform a UE of a time period in which a PRS is transmitted viahigher layer signaling (or, dynamic signaling) in advance. Or, it mayinform the UE of the time period in which the PRS is transmitted byproviding a period/offset/burst length to the UE. If the time period inwhich the PRS is transmitted is included in secured channel occupancytime, an eNB can transmit the PRS. In this case, a burst corresponds toa time period consisting of one or more transmission units (e.g.,subframe).

The UE performs blind detection on the PRS in a time period in which thePRS is indicated to be transmitted using the aforementioned method toperform positioning-related measurement.

As mentioned in the foregoing description, in consideration of asituation that the whole frequency band is divided into narrow frequencybands, CCA is performed on each of the frequency bands to identify achannel state, and channel occupancy time is independently configured,it may inform a UE of a time period in which a PRS is transmitted viahigher layer signaling (or, dynamic signaling) in advance. Or, it mayinform the UE of the time period in which the PRS is transmitted byproviding a period/offset/burst length to the UE.

If a time period in which a PRS is transmitted is included in channeloccupancy time which is secured according to a frequency band, an eNBcan transmit the PRS. In other word, the eNB transmits the PRS duringthe time period configured to transmit the PRS for all of a part offrequency bands, which have secured channel occupancy time, among aplurality of frequency bands. A UE performs blind detection on the PRSin the time period configured to transmit the PRS according to eachfrequency band to perform positioning-related measurement.

The maximum number of frequency bands on which PRS blind detection is tobe performed by a specific eNB at specific timing can be set to a UE.Or, the number of frequency bands capable of performing PRS blinddetection from a specific eNB at specific timing can be set to the UE.And, priority of frequency bands to perform PRS blind detection atspecific timing can be set to the UE.

If a specific eNB is able to configure channel occupancy time to be thesame or to be overlapped on contiguous frequency bands, it may be ableto transmit a single PRS on the contiguous frequency bands according toa contiguous CA scheme. A UE performs blind detection on the single PRSon the contiguous frequency bands in addition to the blind detectionaccording to a frequency band, combines positioning-related measurementresults, and individually or selectively reports the result.

In general, a wireless service provider divides a spatial region intocells of appropriate coverage and makes an eNB belonging to each of thecells perform wireless communication with UEs belonging to the cell tominimize inter-cell interference and permit simultaneous transmissionbetween neighboring cells. By doing so, it may be able to enhanceoverall system performance. This operation may correspond to apreferable operation when LTE system is managed on an unlicensed band.Yet, since LTE nodes (e.g., eNB, UE) on the unlicensed band transmit asignal based on LBT, if a specific node occupies a channel to transmit asignal, a different node determines that the channel is busy accordingto a CCA result. Hence, it is highly probable that it is unable to reusea frequency. Hence, in order to maximize frequency reuse of an LBT-basedLTE system on an unlicensed band, it is preferable to define a(recommended) node group (e.g., an eNB managed by the same serviceprovider) capable of performing simultaneous transmission. In this case,it is necessary for each node belonging to the node group to recognize asignal transmitted by a different node belonging to the node group inthe course of performing CCA and exclude power (or energy) used fortransmitting the signal from power (energy) used for performing the CCA.

In this case, when a specific frequency/time resource is indicated totransmit a PRS and the resource is included in channel occupancy time,if a neighboring eNB configures channel occupancy time and transmitsdata, it may work as interference. As a result, accuracy ofpositioning-related measurement can be degraded.

In order to prevent the interference, it may be able to configure aplurality of eNBs to have a common PRS transmission period/offset/burstlength on a specific frequency band via a predefined coordination or acoordination of eNBs via a signal between the eNBs.

Or, it may be able to configure eNBs not to transmit a PRS or data on aspecific frequency band and specific timing via a predefinedcoordination or a coordination of eNBs via a signal between the eNBs.

Hence, a UE may be able to expect that a data is not transmitted at thetiming at which a PRS is configured to be transmitted.

The UE receives PRS transmission period/offset/burst length informationon a plurality of eNBs and a muting pattern of the timing according to afrequency band (or the whole frequency band). The UE performs blinddetection on a PRS in a time period configured to transmit the PRS toeach eNB to perform positioning-related measurement.

FIG. 13 is a flowchart for an operation according to one embodiment ofthe present invention.

FIG. 13 shows a method of receiving a reference signal for determining aposition in a wireless communication system. The method can be performedby a terminal.

The terminal may receive PRS (positioning reference signal)-relatedconfiguration information transmitted through coordination of at leastone or more unlicensed band cells [S1310]. The PRS-related configurationinformation may include information on a plurality of subbands in theunlicensed band on which the PRS is transmitted and information on a PRStransmission period according to a plurality of the subbands. Theterminal may receive and measure a PRS using the PRS-relatedconfiguration information [S1320]. Subsequently, the terminal may reporta measurement result of the PRS to a serving cell [S1330].

In order for the terminal to receive and measure the PRS, the terminalmay perform PRS blind detection using the PRS-related configurationinformation.

The terminal may receive information on the number of subbands on whichthe PRS blind detection is to be performed from the serving cell. Theterminal may receive information on priority of subbands on which thePRS blind detection is to be performed from the serving cell.

The PRS transmission period information may be common to unlicensed bandcells belonging to the same cell group.

The PRS transmission period information may include a period, offset,and a burst length for which a PRS is transmitted.

The PRS-related configuration information may include information onwhether or not a PRS transmission period is included in channeloccupation time for the one or more unlicensed band cells.

In order for the terminal to receive and measure the PRS, the terminalmay perform PRS blind detection in the channel occupation time.

The PRS-related configuration information may include information on thechannel occupation time and information on the PRS transmission period.

The PRS-related configuration information may be received via downlinkcontrol information through a licensed band cell or an unlicensed bandcell.

If a reservation signal is received in a specific time period, theterminal may determine that a PRS transmission subframe is included inchannel occupation time for the at least one or more unlicensed bandcells.

A PRS, which is transmitted via the at least one or more unlicensed bandcells, may be transmitted in a resource element where a differentunlicensed band cell does not transmit a PRS.

A measurement result of the PRS may be independent of a measurementresult of a PRS transmitted on a licensed band.

So far, embodiments according to the present invention are brieflyexplained with reference to FIG. 13. Yet, the embodiments related toFIG. 13 may alternatively or additionally include at least a part of theaforementioned embodiment(s).

FIG. 14 is a block diagram illustrating a transmitter 10 and a receiver20 configured to implement embodiments of the present invention. Each ofthe transmitter 10 and receiver 20 includes a radio frequency (RF) unit13, 23 capable of transmitting or receiving a radio signal that carriesinformation and/or data, a signal, a message, etc., a memory 12, 22configured to store various kinds of information related tocommunication with a wireless communication system, and a processor 11,21 operatively connected to elements such as the RF unit 13, 23 and thememory 12, 22 to control the memory 12, 22 and/or the RF unit 13, 23 toallow the device to implement at least one of the embodiments of thepresent invention described above.

The memory 12, 22 may store a program for processing and controlling theprocessor 11, 21, and temporarily store input/output information. Thememory 12, 22 may also be utilized as a buffer. The processor 11, 21controls overall operations of various modules in the transmitter or thereceiver. Particularly, the processor 11, 21 may perform various controlfunctions for implementation of the present invention. The processors 11and 21 may be referred to as controllers, microcontrollers,microprocessors, microcomputers, or the like. The processors 11 and 21may be achieved by hardware, firmware, software, or a combinationthereof. In a hardware configuration for an embodiment of the presentinvention, the processor 11, 21 may be provided with applicationspecific integrated circuits (ASICs) or digital signal processors(DSPs), digital signal processing devices (DSPDs), programmable logicdevices (PLDs), and field programmable gate arrays (FPGAs) that areconfigured to implement the present invention. In the case which thepresent invention is implemented using firmware or software, thefirmware or software may be provided with a module, a procedure, afunction, or the like which performs the functions or operations of thepresent invention. The firmware or software configured to implement thepresent invention may be provided in the processor 11, 21 or stored inthe memory 12, 22 to be driven by the processor 11, 21.

The processor 11 of the transmitter 10 performs predetermined coding andmodulation of a signal and/or data scheduled by the processor 11 or ascheduler connected to the processor 11, and then transmits a signaland/or data to the RF unit 13. For example, the processor 11 converts adata sequence to be transmitted into K layers through demultiplexing andchannel coding, scrambling, and modulation. The coded data sequence isreferred to as a codeword, and is equivalent to a transport block whichis a data block provided by the MAC layer. One transport block is codedas one codeword, and each codeword is transmitted to the receiver in theform of one or more layers. To perform frequency-up transformation, theRF unit 13 may include an oscillator. The RF unit 13 may include Nttransmit antennas (wherein Nt is a positive integer greater than orequal to 1).

The signal processing procedure in the receiver 20 is configured as areverse procedure of the signal processing procedure in the transmitter10. The RF unit 23 of the receiver 20 receives a radio signaltransmitted from the transmitter 10 under control of the processor 21.The RF unit 23 may include Nr receive antennas, and retrieves basebandsignals by frequency down-converting the signals received through thereceive antennas. The RF unit 23 may include an oscillator to performfrequency down-converting. The processor 21 may perform decoding anddemodulation on the radio signal received through the receive antennas,thereby retrieving data that the transmitter 10 has originally intendedto transmit.

The RF unit 13, 23 includes one or more antennas. According to anembodiment of the present invention, the antennas function to transmitsignals processed by the RF unit 13, 23 are to receive radio signals anddeliver the same to the RF unit 13, 23. The antennas are also calledantenna ports. Each antenna may correspond to one physical antenna or beconfigured by a combination of two or more physical antenna elements. Asignal transmitted through each antenna cannot be decomposed by thereceiver 20 anymore. A reference signal (RS) transmitted in accordancewith a corresponding antenna defines an antenna from the perspective ofthe receiver 20, enables the receiver 20 to perform channel estimationon the antenna irrespective of whether the channel is a single radiochannel from one physical antenna or a composite channel from aplurality of physical antenna elements including the antenna. That is,an antenna is defined such that a channel for delivering a symbol on theantenna is derived from a channel for delivering another symbol on thesame antenna. An RF unit supporting the Multiple-Input Multiple-Output(MIMO) for transmitting and receiving data using a plurality of antennasmay be connected to two or more antennas.

In embodiments of the present invention, the UE operates as thetransmitter 10 on uplink, and operates as the receiver 20 on downlink.In embodiments of the present invention, the eNB operates as thereceiver 20 on uplink, and operates as the transmitter 10 on downlink.

The transmitter and/or receiver may be implemented by one or moreembodiments of the present invention among the embodiments describedabove.

Detailed descriptions of preferred embodiments of the present inventionhave been given to allow those skilled in the art to implement andpractice the present invention. Although descriptions have been given ofthe preferred embodiments of the present invention, it will be apparentto those skilled in the art that various modifications and variationscan be made in the present invention defined in the appended claims.Thus, the present invention is not intended to be limited to theembodiments described herein, but is intended to have the widest scopeconsistent with the principles and novel features disclosed herein.

INDUSTRIAL APPLICABILITY

The present invention is applicable to wireless communication devicessuch as a terminal, a relay, and a base station.

What is claimed is:
 1. A method of receiving a reference signal forpositioning in an unlicensed band, which is received by a terminal in awireless communication system, comprising: receiving positioningreference signal (PRS)-related configuration information transmittedthrough the coordination of one or more unlicensed band cells, whereinthe PRS-related configuration information comprises information on aplurality of subbands within the unlicensed band on which the PRS istransmitted and information on a PRS transmission period for each of theplurality of the subbands; receiving and measuring a PRS using thePRS-related configuration information; and reporting a measurementresult of the PRS to a serving cell.
 2. The method of claim 1, whereinthe receiving and measuring the PRS comprises performing PRS blinddetection using the PRS-related configuration information.
 3. The methodof claim 2, further comprising receiving information on the number ofsubbands on which the PRS blind detection is to be performed.
 4. Themethod of claim 2, further comprising the step of receiving informationon priority of a subband on which the PRS blind detection is to beperformed.
 5. The method of claim 1, wherein the information on the PRStransmission period is common to unlicensed band cells belonging to thesame cell group.
 6. The method of claim 1, wherein the information onthe PRS transmission period comprises a transmission period, offset, ora burst length of the PRS.
 7. The method of claim 1, wherein thePRS-related configuration information comprises information on whetheror not the PRS transmission period belongs to channel occupation timefor the one or more unlicensed band cells.
 8. The method of claim 7,wherein the receiving and measuring the PRS comprises performing PRSblind detection during the channel occupation time.
 9. The method ofclaim 7, wherein the PRS-related configuration information comprisesinformation on the channel occupation time and information on the PRStransmission period.
 10. The method of claim 1, wherein the PRS-relatedconfiguration information is received through downlink controlinformation via a licensed band cell or an unlicensed band cell.
 11. Themethod of claim 1, further comprising determining that a PRStransmission subframe belongs to channel occupation time for the one ormore unlicensed band cells when a reservation signal is received in aspecific time period.
 12. The method of claim 1, wherein a PRStransmitted through the one or more unlicensed band cells is transmittedon a resource element where a different unlicensed band cell does nottransmit a PRS.
 13. The method of claim 1, wherein the measurementresult of the PRS is independent of a PRS measurement result on alicensed band.
 14. A terminal configured to receive a reference signalfor positioning through one or more unlicensed band cells in a wirelesscommunication system, comprising: an radio frequency (RF) unit; and aprocessor controls the RF unit to: wherein the processor receivespositioning reference signal (PRS)-related configuration informationtransmitted through the coordination of one or more unlicensed bandcells, wherein the PRS-related configuration information comprisesinformation on a plurality of subbands within the unlicensed band onwhich the PRS is transmitted and information on a PRS transmissionperiod for each of the plurality of the subbands, receives and measuresa PRS using the PRS-related configuration information, and reports ameasurement result of the PRS to a serving cell.